Method of making safety type inner tubes



Aug. 5, 1952 A. N. IKNAYAN 2,606,135

METHOD OF MAKING SAFETY TYPE INNER TUBES Original Filed Jan. 2, 1948 2 SHEETSSHEET 1 INVENTOR. 10mm Al. MWJMA/ Aug. 5, 1952 A. N. IKNAYAN METHOD OF MAKING SAFETY TYPE INNER TUBES Original Filed Jan; 2, 1948 2 SHEETS-SHEET 2 I N V EN TOR. 41/7110 A/. M/mm/z B Y AGENT patented Aug. 5, 1952 NIT so STAT es; r v j 1 g 2,606,135 V J. E OD F MAKI G SAFETY-TYPE- INNER TUBES Alfred ,N. Iknayan, Indianapolis, I d. assign t9 United. States Rubber Company,

New ork,

N. Y., a corporation of New. J ersey.

8. Claims.

This invention relates to a method of-making inner tubes. More particularly, the invention re lates to a m t f makin a a et ty n r tube in which the inner tube includes reinforcing cords for the purpose ct increasing the strength and rigidity of the tube wall thereby enhancing the strength of the tire carcass with which the inner tube is associated.

This application is a division of my application Serial No. 290, filed January 2, 194 and now abandoned.

In the operation of automotive vehicles, the hazard of blowouts and quick defiations of pneumatic tires is becoming increasingly dangerous, Dueto the high speed at which automotive vehicles are driven and due to the increased horsepower of the engines for driving the vehicles, the pe f rman e pe ted f t e i c nstentlyincreasing. It is difiicult to provide a pneumatic tire which is blowout-proof. Furthermore, tires frequently receive serious injury in their operation due to one of many causes such as using improper inflation pressures or riding over objects which produce undue distortions to the carcass. Such injuries or weak spots in thecarcass arenot readily apparent even upon careful inspection.

In accordance with the practice of my invention, I provide an inner tube having strain resisting elements and which is capable of forthns ne mat c tirev s to n i e an a d d. ein orc n a an n u an e a a ns failure.

It-is recognized that-various types of safety tubes have been tried out and that even the most successful of the tubes heretofore used commercially'do notprovide a desired insurance against sudden deflation. It is also recognized that greater strength may be imparted to a tire carcassby providing a carcass having a greater number of plies. Such additional plies, however, are not particularly satisfactory becauseany rup: ture or break in the carcass tends to move progressively throughout the thickness of the carcass regardless of the number of plies. Consequently, an increase in carcass thickness is not the whole answer to increased protection. I have found, however, that such increased protection to the carcass may be obtained by utilizing increased plies which are separate and not united as a unit to the carcass. As a result of the use of such a separate unit, a break in the carcass may pro: gress through the entire carcass but will 'not i' 'adily .proceed through a separate unitwhich iassmelesisnt is self-adjus ing w hm hc a s-and assumes i s w s rain resistmeshara v teiistics, 1

I pr ndnner t e. t e erie ip lw-e of which include strain resisting elements and which in combination includes an eaten e;

ubs andthe insets. a i ical gi e a iv Lil e s i er tha the bene t of the. mn w time ma b a n d t l rtn r l have imam! ma t junction tween he exterisib se 1 s l rp t n should beloca d elQI-l thewall 9i the inextensible portion to allow fre'e ends oithe extensible portion to s rye as relief for the str 11 e in elemen w t the inextsns e. Pu

It is ec ize t ath re e s e ertain n gr liners have bee used betweenithe. tiret rc an h o v nt onal inner ube-I Th invention differs from such a cons u hat it is bie i na sp ageai ee o ineretween t e nne tu e andi ec ins au eq t en snc te g een s hat. e tated and-becausefit' w c usually. i the flexin e and ih sb causins' q flsrsni al mor which r sult n hafin andgvcntu tl. fails the inner tube.

Another object of myinventioni to, a nn ru e ich. even. n ..seve re n thecarcass oi the pn matic tire will 119 (1 t9 bridge the brealsandp yenta-hl wout. u h nd ti nsa ire. ubstant al dams d a e n t t u n nbi e w l e are to the operator so that thevehicle may bestop an he r Y nsrzec stlk Under these. i thetireremains 'fullyv-iniiatedand-ma b w ubstant l dis ances o e rebates W111. be ame so xt nsi sas t ause v si u epf ineer tiib' e uch eventua ity it besee found t the t still iiefl tesl w y,thue verco thedan er0 l flniliififiliiqn I These-and t er-onse s ant advanta arse mgr iull n tee f llq i tlon en s eegee intone imnw accom an in dra i nwhich:

m erse w. 1 sectio of, an mile? b made. ac rdiestd m pvelitiofi;

Figure 2 is a transverse. w. ins ceon, m'ngr tube fili anin I wns nr iaiepeace; j

Figure 3 is a transverse view, in section, of an inner tube illustrating a modified form of my invention;

Figure 4 is a perspective view, partly in section, of a band of rubberized plies illustrating the first operation in the method of making the inner tube;

Figure 5 is a transverse View, in section, of a portion of an apparatus upon which the plies forming the band are shaped;

Figure 6 is a transverse view, in section, showing the shaped plies in association with a curing a Figure 7 is a transverse view, in section, of the shaped plies after the curing operation; and

Figure 8 is a transverse view, in section, of the cured plies shown in assembled relation with an uncured strip of rubber forming the extensible portion of the inner tube.

The walls form, in effect, a crown wall supporting the tread area of the tire casing and side walls supporting the side portions of the casing.

With reference to the drawing and in particular to Figure 1, I show an embodiment of my invention in the form of an inner tube I having features as hereinafter described. Essentially, the inner tube I comprises'two plies 2 and 3 of rubberized fabric vulcanized so as to form an annulus or circular tube. In cross section, however, the walls forming the rubberized plies 2 and 3 do not form a complete circle but terminate in free ends 4 and 5 forming less than a complete circle. A rim strip 6 of rubber composition which forms, in effect, a base wall joins the walls of the plies 2 and 3 together to form a complete enclosed air chamber. The junctions i and 8 between the strip 6 and the outer wall of the inner tube l are located in spaced relation from the free ends 4 and 5 respectively The distance of these junctions as defined by the letter A is equal to approximately 20% of the circumferential distance cross-sectionally around the inner tube. This distance represents a measurement taken on the inner tube when it is unmounted and inflated merely sufiiciently to expand the tube to circular shape without any substantial distortion of the tube. While the distance A has been stated to be equal to approximately 20% of the cross sectional circumference of the inner tube, it has also been found that good results may be obtained by maintaining this dimension within a range of from 13 to 27%.

The inner tube l composed of the strain resisting plies 2 and 3 is intended to be of such dimensions that it will fit closely with the interior of the tire casing with which it is intended for assembly. In other words, the inner tube with slight inflation will completely fill th cavity of the tire casing without any substantial strain on the plies 2 and 3 constituting the principal portion of the inner tube I. It is to be understood that a conventional valve assembly (not shown) is intended to be used with the inner tube and in particular in association with the rim strip 6.

Figure 2 illustrates the inner tube in assembled relation with a tire 9 and a rim I0. This tube is shown under normal operating inflation pressure. Under such conditions the rim portion 6 expands into the well of the rim l0 while the remaining portion of the tube lies against the inner wall of the casing in a substantially undistorted or unstretched condition. It will be noted in Figure 2 that the locations of the junctions 1 and 8 defining the meeting points between the rim strip 6 and the outer wall of the inner tube I lie in a position adjacent to the beads of the tire. Also, this junction should lie between the seat of the rim and the outer diameter of the flange of the rim. This zone is indicated by a dimension B in Figure 2. The reason for limiting the location of this junction is that it is essential that the strain resisting portion of the inner tube as defined by the plies 2 and 3 should extend from head to bead of the tire and lie within that zone in which no flexing of the tire occurs while in operation. The distance represented by the letter B indicates this nonfiexing zone.

It is also desirable that the fabric plies 2 and 3 continue beyond the junctions land 8 so as to constitute the free ends 4 and 5. This is essential to eliminate an abrupt junction between the strain resisting plies 2 and 3 and the extensible rim strip 6. By forming the junctions 1 and 8, in effect, along the wall of the ply 2, it is possible to form a better attachment of the rim strip 6 to the outer wall. Furthermore, by this arrangement there is less relative movement at the junction with the result that localized strains are reduced so as to prevent failures at this location, As shown in Figure l, the plies 2 and 2 overlap as they lie within the free ends 4 and 5. The purpose of this overlapping or offsetting is to permit a more gradual tapering of the free edges and to eliminate a more abrupt ending of the reinforcing elements.

Figure 3 illustrates a modification of my invention and shows an inner tube H having plies l2 and [3 of strain resisting elements constituting the principal wall of the inner tube. The walls of the tube terminate in free ends l4 and I5 at the rim region. This modification is essentially the same as that shown in Figure 1 with the exception that a rim strip l6 of extensible rubber composition is attached to the inner wall of the tube in place of the outer wall of the inner tube. Otherwise the general characteristics of the tube including the dimension C is the same as the corresponding features of the tube shown in Figure 1. The advantage of attaching the rim strip [6 to the inner wall of the tube is to permit the strain resisting free ends [4 and 15 to lie against the junction formed by the tire bead and the rim with which it is associated. Ordinarily, there is a slight relative movement between the tire bead and the rim while the tire is in operation. For this reason, the double wall at that junction reinforces the tire assembly at a most critical point thus reducing tire failures. Also, the free ends are not under tension and serve better to resist chafing in this locality.

An inner tube of the principal embodiment of my invention and as illustrated in Figur l is manufactured in accordance with the steps illustrated by Figures 4 to 8 inclusive. Figure 4 shows the make-up of the two plies 2 and 3. Essentially, these plies are formed of layers of cord fabric I1 and [8 in which the cords are spaced 35 ends per inch. Each cord is formed of plied yarn and made from nylon filaments in which the cord has a gage of .020 and having a strength of approximately 25 pounds. A cord of this kind provides a high strength while at the sam time permitting the wall of the tube to be relatively thin. While cords formed of nylon are preferable, comparable results may also. be obtained by utilizin other strain resisting elements such as cotton, rayon, or steel. The direction of the cords of fabric l1 and I8 are diagonal in respect to a circumferentially extending center line. More specifically, the cords lay at an angle so that after the shaping operation hereinafter described the cords will constitute an angle of approximately 45.

In accordance with customary procedure in tire manufacture, the cord fabrics l1 and 18 are solutioned. with rubber and thereafter a layer of rubber composition is applied to both surfaces of each of the fabrics I1 and 18. For example, a layer of rubber composition IQ of a gage .015 inch is applied to the underside of the fabric 11 and a layer of rubber composition 20 of a gage of .045 inch is applied to the outer side of the fabric. ,A layer of rubber composition 2| of .015 gage is applied to the outer side of the fabric 18 while a layer of rubber composition 22 of a .045 gage is applied to the underside of the fabric 18. With the cord fabric thus encased in layers of rubber composition, the two plies 2 and 3 are assembled together in overlapping relation and in flat band form as shown in Figure 4. The purpose of the overlapping relation is to permit a better tapering of the free edges as shown in Figure 1. To complete the band assembly, two strips or ribbons '23 and 24 are applied to the outer surface of the outer ply 2'. These strips or ribbons are intended to increase the thickness of the ply at specific circumferential regions in order to serve as a buffing strip as hereinafter described.

When the two plies 2 and 3 are thus assembled, they are placed on a drum as shown in Figure 5 for the purpose of expanding the assembled layers and shaping them closely to the conformity of an annulus. The drum illustrated diagrammatically comprises end members 25 and 26 having a cylindrical cover 21. An expansible air bag 28 is positioned centrally on the drum in a deflated substantially flat condition, and the plies 2 and 3 are positioned over the drum and over the deflated air bag. A hand hole 29 through the end member 25 permits an operator to inflate the air bag by means of the airbag valve 30.

Asa result of the inflation, the air bag blows circular in cross-section and the assembled plies 2 and 3 are shaped as shown by the dot and dash lines. Preferably the air bag 28 includes reinforcing cords so as to better control its uniformity of expansion.

While I have shown a special means for shaping the plies 2 and 3, it is to be understood that various methods of shaping may be employed. Forexample, theplies may be shaped in a vacuum apparatus such as used in the conventional shaping of pneumatic tires. After allowing the assembly to be held in this expanded shape for a few moments, the air bag is deflated and the assembled plies are removed from the drum. Thereafter a flexible curing bag 3! (Figure 6) is collapsed and inserted into the partially shaped and assembled plies 2 and 3. Next the curing bag with the plies assembled thereon is placed in a vulcanizer and the plies are vulcanized. When the curing bag is-removed, the plies 2 and 3 and the associated components form an-integral unit constituting an annulus having a circular cross section and having open free ends in the region of the rim. This completed unit of the assembly isshown in Figure '7.

During the curing operation the strips 23 and 24 merge with the wall of the inner tube and form circumferentially extending bumps orridges i to obtain good adhesion, to buff-a circumferential strip as defined by the ridges 32 and 33. When the buffing operation is complete, cement is applied to that area and the rim strip 6 is assembled, with its marginal portion in contact relationship.

In order to prevent adhesion between the free ends 4 and 5 of the tube with the rim strip, that portion of the rim strip or of the free ends or both, may be coated with a non-adherent material such as soapstone or the like, thus preventing adhesion during vulcanization. In accordance with conventional practices, a valve stem (not shown) may be attachedto the rim strip '6. When this operation is completed, the assembly is again placed into a mold and the tube is vulcanized. The resulting assembly is illustrated in Figure 1.

When the tube is completed, its outer appearance is not readily distinguishable from the conventional tube. Its total wall thickness is in the order of .150 inch and it may be even less than this dimension. The advantages of such a tube have been well demonstrated and the two additional plies constituting the tube itself increase the carcass strength of the tire by approximately 50%. When nylon is used as the strain resisting elements, this strength is still higher relative to the carcass. When steel cord is used in the inner tube, the strength of the tube becomes even greater than the strength of the tire carcass. Therefore, the protective value of the inner tube is evident in that it will retain the inflated con dition of the tire notwithstanding complete failure of the tire itself.

Many tests have been made to determine the practicability and performance of the inner tube made in accordance with my invention. For example, in one of these tests an inner tube was mounted in a 650-16 tire-casing having a rupture extending through the tire carcass in the form of a letter X and the size of the rupture was 2% inches by 2 inches. This tire was driven a distance of 96 miles before the operator became aware of a bumping of the tire. The vehicle was driven at the rate of '70 miles per hour ona paved road. At 117 miles the tire started to throw its tread and at this point the tube failed and the deflation of the tube was sufiiciently slow to permit the vehicle to be easily handled until reaching a complete stop. An inspection of the tire showed that a fabric break extended 2 inches above the bead around the tread of the tire and to a point 2 inches above the opposite bead. Attempts have been made to repeat this test using conventional inner tubes and using a similar ruptured casing having a break size of 2 5; inches by 2 inches. The tire ran only 34 milesbefore the tube failed completely and without warning causing the vehicle to swerve badly. An inspection of the tire showed that the size of the rupture had increased to .3 inches by 2 inches.

In, order to show the advantages of the present tube in connection with its puncture resisting 'characteristicsLa tire having a tubeof my invention was punctured by forcing into the casing and through the tube a nail of a diameter of .134 inch. This tire was driven a, distance of 330 miles at from 45 to 50 miles per hour without failure and without lossof air. Similar testswere conducted using nails having diameters of .148, .164, .209, .229, .248 and .265. In each case the tires were driven a distance of 330 miles Without failure or deflation of the inner tubes. Using a conventional inner tube and with a nail of the 7 size .134 driven into the tire and through the inner tube, the tube was completely deflated after driving the vehicle 19 miles.

A number of other tests have been conducted and in each case the superiority of the inner tube of my invention has been demonstrated to be much greater in resistance to punctures and in its capability of supporting a damaged casing with its subsequent beneficial result to the protection of the tire casing and inner tube and to the vehicle and its occupants.

As thus shown and described, it is believed that a novel tube has been produced which in appearance and use is substantially the same as that of a conventional inner tube yet which serves as a safety factor for the vehicle and for its occupants throughout a wide range of failures of the tire carcass.

While reference is made to rubber and rubber compositions, it is to be understood that the invention contemplates synthetic rubber as well as natural rubber. By synthetic rubber I refer to those modified butadiene-1,3-derived rubber materials which lie within the class of neoprene (polychloroprene), Buna S (rubber copolymer of butadiene-L3 and styrene), and Buna N (rubbery copolymer of butadiene-l,3 and acrylonitrile), Butyl (rubbery copolymer of a major proportion of a monolefine, e. g., isobutylene, with a minor proportion of a conjugated 1,3-oliene,

e. g., isoprene). 1

Having thus described my invention, what I claim and desire to protect by Letters Patent is:

1. The method of making inner tubes comprising the steps, forming a fiat annular band of a plurality of rubberized plies of strain resisting elements, shaping the band to form a partially circular shape in cross-section, vulcanizing the shaped band, and attaching an extensible strip of rubber composition to the edge portions of the shaped band to form an enclosed chamber.

2. The method of making inner tubes comprising the steps, forming a flat annular band of a plurality of rubberized plies of strain resisting elements, shaping the band to form a partially circular shape in cross-section, vulcanizing the shaped band, and attaching an extensible strip of rubber composition to the shaped band at a point spaced from the marginal edges of the band to allow free edge portions of the band to extend beyond the junction formed between the band and the extensible strip.

3. The method of making inner tubes comprising the steps, forming a flat annular band of a plurality of rubberized plies of strain resisting elements, locating one of said plies in off-set relation to its adjacent ply for constituting tapered edges, shaping the band to form a partially circular shape in cross-section, vulcanizing the shaped band, and attaching an extensible strip of rubber composition to the edge portions of the shaped band to form an enclosed chamber.

4. The method of making inner tubes comprising the steps, forming a flat annular band of a plurality of rubberized plies of strain resisting elements, attaching a ribbon of rubber composition to one of the exposed surfaces of the plies at a point spaced from the marginal edge of the ply, shaping the band to form a partially circular shape in cross-section, vulcanizing the shaped band, and attaching an extensible strip of rubber composition to the band at the region of the ribbon to form an enclosed chamber.

5. The method of making inner tubes comprising the steps, forming a flat annular band 01 a plurality of rubberized plies of strain resisting elements, attaching a ribbon of rubber composition to one of the exposed surfaces of the plies at a point spaced from the marginal edge of the ply, shaping the band to form a partially circular shape in cross-section, vulcanizing the shaped band, buffing that region of the shaped band upon which the ribbon is located, and attaching an extensible strip of rubber composition to the band at the region of the ribbon to form an enclosed chamber.

6. The method of making inner tubes comprising the steps, forming a fiat annular band of a plurality of rubberized plies of strain resisting elements, attaching a ribbon of rubber composition to one of the exposed surfaces of the plies at a point spaced from the marginal edge of the ply, shaping the band to form a partially circular shape in cross-section, vulcanizing the shaped band, bufiing that region of the shaped band upon which the ribbon is located, attachingan extensible strip of rubber composition to the band at the region of the ribbon to form an enclosed chamber, and vulcanizing the extensible strip of rubber composition.

7. The method of making inner tubes comprising the steps, forming a fiat annular band of a plurality of rubberized plies of strain resisting elements, shaping the band to form a partially circular shape in cross-section, vulcanizing the shaped band, attaching an extensible strip of rubber composition to the shaped band at a point spaced from the marginal edges of the band to allow free edge portions of the band to extend beyond the junction formed between the band and the extensible strip, treating the free edge portions to prevent adhesion between the free edge portions and the shaped band, and vulcanizing the extensible strip of rubber composi tion.

8. The method of making imier tubes comprising in combination the steps of forming a flat annular band of a plurality of rubberized plies of strain-resisting elements, disposing said band over an inflatable collapsed curing bag, inflating the bag to expand and shape the band to form a partially circular shape in cross-section, vulcanizing the shaped band on said curing bag, removing said curing bag, attaching an extensible strip of vulcanizable rubber composition to the edge portions of the shaped vulcanized band to form an enclosing chamber, and vulcanizing the extensible strip of rubber composition.

ALFRED N. IKNAYAN.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 836,772 Marks Nov. 27, 1906 1,657,052 Webster Jan. 24, 1928 1,818,710 Hannon Aug. 11, 1931 2,231,182 Eger Feb. 11, 1941 2,338,235 Eger Jan. 4, 1944 

1. THE METHOD OF MAKING INNER TUBES COMPRISING THE STEPS, FORMING A FLAT ANNULAR BAND OF A PLURALITY OF RUBBERIZSED PLIES OF STRAIN RESISTING ELEMENTS, SHAPING THE BAND TO FORM A PARTIALLY CIRCULAR SHAPE IN CROSS-SECTION, VULCANIZING THE SHAPED BAND, AND ATTACHING AN EXTENSIBLE STRIP OF RUBBER COMPOSITION TO THE EDGE PORTIONS OF THE SHAPED BAND TO FORM AN ENCLOSED CHAMBER. 